Abstract
This study evaluated the opportunities and challenges of using drones to obtain multispectral orthomosaics at ultra-high resolution that could be useful for monitoring large and heterogeneous burned areas. We conducted a survey using an octocopter equipped with a Parrot SEQUOIA multispectral camera in a 3000 ha framework located within the perimeter of a megafire in Spain. We assessed the quality of both the camera raw imagery and the multispectral orthomosaic obtained, as well as the required processing capability. Additionally, we compared the spatial information provided by the drone orthomosaic at ultra-high spatial resolution with another image provided by the WorldView-2 satellite at high spatial resolution. The drone raw imagery presented some anomalies, such as horizontal banding noise and non-homogeneous radiometry. Camera locations showed a lack of synchrony of the single frequency GPS receiver. The georeferencing process based on ground control points achieved an error lower than 30 cm in X-Y and lower than 55 cm in Z. The drone orthomosaic provided more information in terms of spatial variability in heterogeneous burned areas in comparison with the WorldView-2 satellite imagery. The drone orthomosaic could constitute a viable alternative for the evaluation of post-fire vegetation regeneration in large and heterogeneous burned areas.
Highlights
Natural hazards, such as wildfires, constitute a serious global concern that is expected to increase in the future [1] mainly due to global warming predictions and changes in land use [2,3]
The main objective of this study is to evaluate the feasibility of using a rotor-based unmanned aerial vehicles (UAVs) with an on-board multispectral sensor (Parrot SEQUOIA) to obtain a multispectral orthomosaic at ultra-high spatial resolution, which could be useful for forestry management purposes in a heterogeneous and large burned area (3000 ha)
This study evaluated the strengths and limitations of using a rotor-based UAV equipped with a novel multispectral camera (Parrot SEQUOIA) to conduct a field survey of a large (3000 ha) and heterogeneous burned surface
Summary
Natural hazards, such as wildfires, constitute a serious global concern that is expected to increase in the future [1] mainly due to global warming predictions and changes in land use [2,3]. The increasing severity and recurrence of large forest fires in Mediterranean Basin ecosystems [4] can lead to severe long-term land degradation, including desertification [5,6]. Advances in geospatial technologies have led to an increase in the utilization of remote sensing techniques [3], which represent a major opportunity for conducting post-fire surveys in large and heterogeneous burned ecosystems [8]. High spatial resolution satellite imagery, such as that provided by Deimos-2, GeoEye-2, QuickBird or WorldView-2 on-board sensors, among others, have been used to assess post-fire regeneration in terms of fractional vegetation cover [8], species richness [9] or the basal area of tree species [10]. Satellite imagery shows certain weaknesses that could limit its applicability in the post-fire monitoring of highly heterogeneous and dynamic areas. The revisit periods of satellite platforms cannot be user-controlled for short-term time series monitoring
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